docs: def load_metadata(refresh_cache=False):
      """Returns a graph representing meta-data for all Project Gutenberg texts.
      Pertinent information about texts or about how texts relate to each other
      (e.g. shared authors, shared subjects) can be extracted using standard RDF
      processing techniques (e.g. SPARQL queries). After making an initial remote
      call to Project Gutenberg's servers, the meta-data is persisted locally.
  
      """
      cache = get_metadata_cache()
  
      if refresh_cache:
          cache.refresh()
  
      if not cache.is_open:
          cache.open()
  
      return cache.graph